Trace-analysis is one of the primary tools for developing and monitoring high performance semiconductor chips. In trace analysis, events of interest occurring during execution of a software program are monitored to determine how a hardware device performs during such events. It is also desirable to monitor a chip's performance after the debugging process is completed. Different types of information may be recorded during the trace, including instruction op-codes, memory addresses accessed, input, and output. The trace information is written to memory, where it can be analyzed by the user.
U.S. Pat. No. 5,944,841 describes an instruction tracing mechanism where records of instruction tracing are stored to a trace buffer. A tracer pointer points to entries in the tracer buffer. When the trace buffer is full, the trace data is written to another storage device, such as a disk drive or another computer system.
U.S. Pat. No. 5,884,023 describes a tracing scheme where trace information is written to a predetermined trace memory when a predefined trigger occurs. When the trace memory is full, the data in the trace memory is transferred to the test host, thus freeing space in the trace memory.
Since the trace memory is shared with the memory required to store a software application, it would be advantageous to be able to place the trace buffer anywhere and adjust it's size programmatically. None of the prior art discusses a mechanism where the trace buffer's size may be adjusted programmatically. It is an object of the invention to provide a programmable circular buffer for storing trace data.
Another object of the invention is to provide a bus analyzer capable of performing logic analyzer functions on both the global bus and the I/O bus of a chip.